Honeywell Engines, Systems & Services has developed the Advanced Combustion Tool (ACT) CFD process to rapidly analyze the performance of a combustor configuration from a given fuel injector, CAD geometry and engine cycle information. ACT integrates and streamlines the traditional steps of generating and specifying geometry, mesh, physical models, boundary conditions, initial conditions, convergence criteria and post-processing. Notably, ACT utilizes several key features to reduce cycle time and improve fidelity in the CFD analysis process: a high-pressure spray diagnostic facility to obtain fuel droplet boundary conditions, feature-based macros to parametrically automate geometry and mesh generation, preprocessors to simplify and standardize boundary condition and physical model specification, and post-processors to provide graphical and analytical responses. This integrated process for CFD modeling and optimization is the subject of this paper. A demonstration of this process is the numerical prediction of the TFE731-60 combustor flowfield on a 30 degree sector model compared to experimentally measured results.

In this paper, 3D unsteady and mixing plane CFD simulations including the mainstream full stage on two tested configurations plus a third cavity geometry variance are reported. The sector models were run at test conditions and compared with the corresponding matched Network 1-D flow model to derive the sensitivity of HPT stage forward disc cavity platform axial overlap geometry and supplied purge flow to cavity ingestion dynamics. The first configuration includes no axial overlap (i.e. ΔX/ΔR = 0); the second configuration increases axial overlap by 70% (ΔX/ΔR = 1.82); the third configuration has a larger rim cavity axial spacing and a smaller platform axial overlap (i.e. ΔX/ΔR = 1.67). The unsteady and mixing plane 3D CFD models of the three configurations are run across supplied purge flows ranging from nominal to 35% of the nominal. This was done to obtain a good comparison and to justify the need for unsteady solutions in disc cavity ingestion studies. For each configuration, the CFD predicted mainstream pressure pulse decay profile inside the cavity along with absolute, relative, and static temperatures related to the amount of ingestion that mixes with the supplied flow at several radial heights in the cavity are extracted on a time-averaged and pitch-wise averaged basis. The applied CFD-Network process yields cavity sealing effectiveness versus supplied purge flow and validates platform conductance factors used in 1-D Network flow model. In particular, the unsteady CFD results for the tested configurations were able to reproduce the Network-matched rim cavity effectiveness data at the critical location more closely. The sensitivity results indicate that although, the zero overlap geometry (configuration-1) has insufficient purge flow as evident by the low upper cavity effectiveness, the amount becomes sufficient as the platform axial overlap increases for configuration-2. The influence of increasing rim cavity axial spacing (configuration-3) allows for the same effectiveness to be achieved under a smaller platform axial overlap and lower purge flow supply.

With gas temperatures far exceeding the melting point of nickel-base alloys, advanced cooling schemes are essential to meet the desired mission life of turbine airfoils. Naturally, combustion systems produce gas-temperature non-uniformity in the exiting flowfield. Downstream turbine components must be tolerant to the maximum anticipated gas temperatures. On the other hand, excessive use of cooling air reduces engine efficiency and compromises combustor durability. Throughout gas turbine design history it has been the desire of Turbine Aerodynamicists to be able to compute combustor hot streak migration and mixing through multiple turbine airfoil stages. Typically, hot streak migration studies have been performed using (a) mixing-plane models between rotating and stationery domains or (b) unsteady simulations in which the flowpath annulus is represented by a segment containing airfoil counts that are integer multiples in each blade row or (c) Non-Linear Harmonic methods. With the development of highly-parallelized Computational Fluid Dynamic (CFD) codes driving high performance computer clusters simulation of combustor hot streak migration through multiple High Pressure (HP) turbine stages using an unsteady, 360° (full-annulus) model can be achieved. To this end, Honeywell, in collaboration with Numeca Corporation, has performed a study to evaluate the state-of the art for computation of the effect on second-stage HP turbine nozzle metal temperatures of combustor hot streaks migrated through the first-stage of a two-stage HP turbine.

This paper is a continuation of a previous comparison dealing with URANS-based validation of the ASU-Honeywell turbine stage mainstream/disc-cavity interaction rig data. Here, the validation is with a CFD code named PowerFLOW which is based on the Lattice Boltzmann Method (or LBM). Transient LBM simulations were conducted across the previously published purge flows (Cw of 1540 to 6161), and at the higher mainstream flow condition of 2300 cfm (1.086m3/s). Sensitivity of convergence on results was investigated by increasing the number of revolutions, as well as by varying the passive scalar and temperature difference assumptions between mainstream and purge flow. Results indicate that at lower purge flow, LBM was able to significantly improve validation of sealing effectiveness measurements. For the intermediate purge flows, however, there is a departure from what the data shows. Finally, at the higher purge flow cases, LBM prediction improves at the outer radial location as compared to URANS. Moreover, on pressure validation, it has closed the gap in matching the measured steady pressures inside the lower disc cavity except at the highest purge flow. In the critical upper rim cavity, the gap between the two methods closes as purge flow increases. The outcome from this comparative tool validation study is that at the low critical purge flow case where ingestion is most critical as well as at the upper rim cavity location, sealing effectiveness predictions were significantly improved. The paper also discusses the current limitations of LBM.

The amount of cooling air assigned to seal high pressure (HP) turbine rim cavities is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disk or cover plate life. Excessive purge air, on the other hand, adversely affects performance. This paper is a continuation of the authors' work on ingestion reported by Mirzamoghadam et al. (2008) (“3D CFD Ingestion Evaluation of a High Pressure Turbine Rim Seal Disk Cavity,” ASME Paper No. GT2008-50531), where the main focus of that investigation was to qualitatively describe ingestion driven by annulus circumferential pressure asymmetry under constant annulus conditions and rotational speed. In this paper, the research team investigated the variation of annulus circumferential pressure fluctuation and rotational speed on the double overlap platform rim seal cavity reported in part-1. The outcome from this study was to map out the resulting nondimensional minimum sealing flow (minimum value of Cw or Cw,min) as it relates to entrained ingestion in the absence of cavity cooling flow (Cw,ent). As was done in part-1, the runs were made with 3D computational fluid dynamics (CFD) in setup/run mode option using Fine/Turbo. At two rotational speeds, annulus conditions were varied by reducing turbine inlet pressure (i.e., mass flow) from the baseline operating condition, and the resulting pressure fluctuation was quantified. In addition, an investigation to assess the selected aft-located mixing plane steady state solution for this study as compared to the forward-located steady run was performed using unsteady (nonlinear Harmonics) CFD as the referee. The results yielded the linear decrease in Cw,ent at fixed rotational Reynolds number as annulus Reynolds number was decreased. Moreover, the rate of change in entrained flow sharply increases with increase in rotational Reynolds number. As annulus mass flow is reduced to a critical value defined by annulus-to-rotational Reynolds number ratio, the CFD prediction for Cw,ent converges to the turbulent boundary layer entrainment solution for the rotor, and Cw,min reverts to the rotational Reynolds number dominating region. The results from this study were compared to what has been observed by a previous study for a single overlap platform geometry. The resulting design curve allows insight in relating cavity purge flow requirements versus turbine cycle parameters which could lead to better efficiency.